codegen error: The left-hand side has been constrained to be non-complex, but the right-hand side is complex

I am new to matlab and am trying to compile legacy matlab code into C. I come across the following error when doing so:

??? The left-hand side has been constrained to be non-complex, but the right-hand side is complex. To
correct this problem, make the right-hand side real using the function REAL, or change the initial
assignment to the left-hand side variable to be a complex value using the COMPLEX function.

The code that it complains on is in the comments of the code below:

function [z_out,ovf_flag,ovf_cnt] = fxpt_sgn_saturate(z_in,Nb_out)
Nb_out=(Nb_out<=0)+(Nb_out>0)*Nb_out;
max_val =  2^(Nb_out-1)-1;
min_val = -2^(Nb_out-1);
ovf_cnt = 0;
tmp_ind = find(real(z_in) > max_val);
z_in(tmp_ind) = max_val+1j*imag(z_in(tmp_ind)); // ERROR OCCURS HERE
ovf_cnt = ovf_cnt + numel(tmp_ind);
tmp_ind = find(real(z_in) < min_val);
z_in(tmp_ind) = min_val+1j*imag(z_in(tmp_ind));
ovf_cnt = ovf_cnt + numel(tmp_ind);
tmp_ind = find(imag(z_in) > max_val);
z_in(tmp_ind) = real(z_in(tmp_ind))+1j*max_val;
ovf_cnt = ovf_cnt + numel(tmp_ind);
tmp_ind = find(imag(z_in) < min_val);
z_in(tmp_ind) = real(z_in(tmp_ind))+1j*min_val;
ovf_cnt = ovf_cnt + numel(tmp_ind);
z_out = z_in;
ovf_flag = ~(ovf_cnt==0);
return

I don't particularly understand the code well. Any ideas how to fix this issue?

Thanks

Answer 1

[Walter Roberson]

Before your line

z_in(tmp_ind) = max_val+1j*imag(z_in(tmp_ind)); // ERROR OCCURS HERE

do

z_in = complex(z_in, zeros(size(z_in), class(z_in)) );

The issue is that the z_in you are passing in to the routine has been deduced as being non-complex, but you are trying to store complex values in the array.

If you are expecting that z_in should be already complex, then do not do the above change: instead you need to go up a level to where you are calling the routine, and figure out why it does not know that it is complex.

[ChipMonk]

thank you

Answer 2

[John BG]

Hi ChipMonk

Now your translation moves, but I had to randi variables Nb_out and z_in with guessed sizes:

Nb_out=(Nb_out<=0)+(Nb_out>0)*Nb_out;
max_val =  max(max(2^(Nb_out-1)-1));
min_val = min(min(-2^(Nb_out-1)));
ovf_cnt = 0;
tmp_ind = find(real(z_in) > max_val);
z_in(tmp_ind) = max_val+1j*imag(z_in(tmp_ind)); % now ok
ovf_cnt = ovf_cnt + numel(tmp_ind);
tmp_ind = find(real(z_in) < min_val);
z_in(tmp_ind) = min_val+1j*imag(z_in(tmp_ind));
ovf_cnt = ovf_cnt + numel(tmp_ind);
tmp_ind = find(imag(z_in) > max_val);
z_in(tmp_ind) = real(z_in(tmp_ind))+1j*max_val;
ovf_cnt = ovf_cnt + numel(tmp_ind);
tmp_ind = find(imag(z_in) < min_val);
z_in(tmp_ind) = real(z_in(tmp_ind))+1j*min_val;
ovf_cnt = ovf_cnt + numel(tmp_ind);
z_out = z_in;
ovf_flag = ~(ovf_cnt==0);

.

comment: it didn't move until I added max(max()) and min(min()) to your variables max_val and min_val because as you were generating them, max_val and min_val had exactly same size as Nb_out that then it crashed when attempting to use max_val and min_val as thresholds.

if you find this answer useful would you please be so kind to mark my answer as Accepted Answer?

To any other reader, please if you find this answer of any help solving your question,

please click on the thumbs-up vote link,

thanks in advance

John BG

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